Remembering information is critical in our daily lives, and impairments of memory are profoundly disturbing. These observations motivate research to understand the brain mechanisms involved in normal memory and the types of pathology that produce amnesia. Animal models are especially useful in this endeavor, and experiments with rats are proposed because of the scarcity of monkeys. The experiments are designed to describe the characteristics of the amnesic syndrome seen in rats following damage to different temporal lobe structures, compare these to those seen in primates and humans, and use single unit recordings as a converging operation to examine the role of the hippocampus in normal memory processing. The neuroanatomical focus is on the hippocampus, its external projections through the fimbira-fornix, and the amygdala. The behavioral analyses look at memory for the following types information: the duration of an ongoing event; the duration of an already completed event; spatital locations as compared to cues; procedures; trial unique stimuli as compared to often repeated stimuli. The electrophysiological recordings are made from complex spike units in theta units in the pyramidal cell layer of the hippocampus while rats perform a delayed conditional discrimination, the type of task in which performance is impaired following lesions of the hippocampus. The activity of these units is correlated with the mnemonic aspects of the task (such as the relevant, nonspatial discriminative stimuli; registration, storage, and retrieval of information; correct and incorrect responding, etc.). Together, these experiments help determine the ways in which temporal lobe structures process memory, and the types of memory dysfunctions seen after pathology in them.